The usual method of ice fishing entails the making of a hole through the ice and lowering a fish line and baited hook or lure through the hole into the water below the ice. Ordinarily a single fisherman will fish in more than one such hole and will use a tip up to signal when the line has been pulled down by a fish. When using a tip-up, the line is attached to a spool located in the water below the tip-up. When a fish pulls on the line the spool rotates to release the signal flag which swings up. One disadvantage of such tip-ups is that a rod and reel cannot be used, and moreover, relatively heavy fish line is required because of the difficulty in playing a fish without a rod and reel.
Another problem which commonly occurs during ice fishing is that the water in the hole freezes over and prevents the free movement of the line into and out of the water. Attempts to alleviate this problem have included the pouring of oil or other antifreeze liquid into the hole in the ice. However, this method pollutes the water and such antifreeze liquids do not remain within the hole for any appreciable length of time when the water surface level varies or when the antifreeze liquid is miscible with water.
Still another problem encountered by ice fishermen is that of line wear and breakage caused by the line dragging across the sharp edges of the ice as the fish pulls the line under the ice. This problem is particularly acute while fighting relatively large game fish.